This invention relates generally to magnetic disk drive systems and, more particularly, to a magnetic disk drive system in which the write element leads the read element in the tangential direction of rotation of the magnetic disk.
A typical read/write head in a hard disk drive consists of a read element that leads a write element in the tangential direction of rotation of the magnetic disk. The read head goes over a particular part of the rotating disk before the write head. During customer write operation, the write process must terminate before the read head reaches the servo wedge leaving a gap equals to the length of the read to write head distance. The read element and the write element cannot both be operated at the same time due to magnetic and electrical noise and interaction. Moreover, an additional gap must be added to allow time for the disturbance to decay due to switching from write mode to read mode, known as write to read recovery. As seen in the read/write head 10 of FIG. 1, a read head 12 leads the write head 14 in the tangential direction 16 over the magnetic disk. In FIG. 1A, the write head 14 has just gone over the previous servo wedge or servo identification (SID) region. As the head 10 moves across the data sector, the write head 14 must terminate at location 20 to allow time for the disturbance due to switching to decay (W/R recovery) and to leave a gap equal to the length of the read to write head distance (R/W separation), as seen in FIG. 1B. See, e.g., U.S. Pat. Nos. 5,760,983 and 6,219,194, and U.S. Patent Publication No. 2005/0057837. The total gap represents a loss of area for write operation, and can typically be as much as 30-50% of the total servo overhead. The overall sequential data rate is reduced by the same amount due to this gap.